Routing devices within a network, often referred to as routers, maintain routing information that describe available routes through the network. Upon receiving an incoming packet, the router examines information within the packet and forwards the packet in accordance with the routing information. In order to maintain an accurate representation of the network, routers exchange routing information in accordance with one or more defined routing protocol, such as Interior Gateway Protocol (IGP) within an autonomous system (AS) or Border Gateway Protocol (BGP) between ASs.
Multi-Protocol Label Switching (MPLS) is a suite of protocols used to engineer traffic patterns within Internet Protocol (IP) networks. By utilizing MPLS, an ingress or root node can request a path through a network to an egress or leaf node, i.e., a Label Switched Path (LSP). An LSP defines a distinct path through the network to carry MPLS packets from a source connected to the ingress node to a receiver connected to the egress node. Each router along a LSP allocates a label and propagates the label to the closest upstream router along the path. Routers along the path cooperatively perform MPLS operations to forward the MPLS packets along the established path. A variety of protocols exist for establishing LSPs, e.g., Label Distribution Protocol (LDP) and the Resource Reservation Protocol with Traffic Engineering extensions (RSVP-TE).
Some implementations make use of multipoint LSPs, e.g., Point-to-Multipoint (P2MP) LSPs or Multipoint-to-Multipoint (MP2MP) LSPs, in which a path is established through a network from one or more ingress nodes to two or more egress nodes. Multipoint LSPs are commonly used, for example, to distribute multicast traffic. Multipoint extensions of protocols exist for establishing multipoint LSPs, e.g., multipoint extensions of LDP (mLDP). In mLDP, a multipoint LSP may be established according to an egress-initiated signaling model in which each of the egress nodes initiate label information for the multipoint LSP that is propagated upstream through one or more intermediate transit routers along a path toward the root node. The label information for the multipoint LSP includes a label of the sending node allocated for the multipoint LSP and a forwarding equivalence class (FEC) that uniquely identifies the multipoint LSP based on the root node address and an opaque value.
Upon any failure at the root node, the entire multipoint LSP will be torn down and then reestablished between the egress nodes and a changed root node using a new FEC based on the new root node address. For many multicast applications, such as IP television (IPTV), restoring service to multiple receivers by rebuilding the entire multipoint LSP after any root node failure takes too long to maintain a good user experience.